I’m trying to use the icon element, and I select the “standalone icon with border and optional caption” as my icon style.
There is a field that says “icon size” but it doesn’t do anything to the icon. It only makes the border have a larger radius around the icon. The icon stays tiny.

I tested the option on my test server and it works for me. I guess some other css code overwrites the icon inline styles and thus the “font size” option doesn’t work for you. Please post a link to your icon/website and we’ll look into it.